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Distal humeral endoprosthesis- Stanmore implants custom implant for revision

    Overview

    Learn the Distal humeral endoprosthesis: Stanmore implants custom implant for revision surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Distal humeral endoprosthesis: Stanmore implants custom implant for revision surgical procedure.
    Resection of solitary renal osseous metastases has been proven to offer a survival benefit to patients: (https://online.boneandjoint.org.uk/doi/pdf/10.1302/0301-620x.82b1.0820062).
    Endoprosthetic replacement following excision of metastases has also been shown to restore and preserve function and relieve pain and is advocated in patients with estimated survival greater than the time to rehabilitate i.e. greater than 6-12 months. Careful patient selection by way of thorough pre-operative clinical and radiological assessment plus liaison with oncology teams is essential to identify those patients most likely to benefit from such major surgery and to exclude those in whom the risks outweighs the potential benefits.
    Purely diaphysial bone tumours and intercalary endoprosthetic replacements are rare; at the Royal Orthopaedic Hospital they represent 3% of endoprosthetic replacements. Aseptic loosening is the most common cause of mechanical failure of intercalary endoprosthetic replacements which necessitates challenging revision surgery to preserve function and control pain. Revision of modular intercalary endoprostheses may only require the loose end of the prosthesis to be revised, preserving the integrated portion of the implant, as in this case. (https://www.researchgate.net/profile/Sammy_Hanna2/publication/51213976_Custom_endoprosthetic_reconstruction_for_malignant_bone_disease_in_the_humeral_diaphysis/links/0f31752f6515fdca14000000/Custom-endoprosthetic-reconstruction-for-malignant-bone-disease-in-the-humeral-diaphysis.pdf)
    Distal humeral endoprostheses are very uncommon implants. They typically utilise a cemented ulna component and a hinge mechanism to replace the humero-ulna joint, however in this case we were able to preserve the epicondylar attachments for the stabilising ligaments thus only a hemiarthroplasty was required. This implant has a silver coating (Agluna) to prevent prosthetic infection and hydroxyapatite attachment plates for the medial and lateral epicondyles to achieve osseointegration in an attempt to avoid recurrent aseptic loosening.


    Indications

    INDICATIONS
    The indications for the index intercalary endoprosthetic replacement was to reconstruct a segmental humeral defect after resection of a solitary renal cell carcinoma metastasis, which is known to improve overall patient survival. Aseptic loosening is the most common indication for revision of humeral intercalary endoprostheses (other failure mechanisms may include infection, fracture, local recurrence). The implant is fabricated in two modular halves and bolted together after cementation proximally and distally. As described by McGrath et al. in 2011, revision surgery is facilitated by exchange only of the loose component, the well fixed component may be left in-situ as a new component can be manufactured that bolts into the well fixed component, which preserves bone stock. Where cortical bone around the site of loosening is adequate intra-operative dismantling of the modular prosthesis, debridement and re-cementation of the loose component is recommended (https://www.researchgate.net/profile/Sammy_Hanna2/publication/51213976_Custom_endoprosthetic_reconstruction_for_malignant_bone_disease_in_the_humeral_diaphysis/links/0f31752f6515fdca14000000/Custom-endoprosthetic-reconstruction-for-malignant-bone-disease-in-the-humeral-diaphysis.pdf).
    If there is concern regarding stability of fixation, exchange of the loose component to a custom made intercalary prosthesis with hydroxyapatite coated extra-cortical plate (https://online.boneandjoint.org.uk/doi/abs/10.1302/0301-620x.99b12.bjj-2017-0213.r1). Where bone is inadequate for further fixation joint replacement, as in this case, is advocated.
    SYMPTOMS & EXAMINATION
    This patient was presented with with insidiously worsening pain in the arm and reduced elbow function five years after having a solitary renal metastasis resected and a modular intercalary endoprosthetic replacement. Dressing and washing were very uncomfortable, and he required a sling for comfort.
    IMAGING
    Radiographs showed gross loosening of the distal portion of the intercalary prosthesis but no obvious loosening of the proximal implant-cement interface. Satisfactory integration was confirmed proximally with CT. Routine serum inflammatory markers (CRP, ESR) were normal, thus no pre-revision aspiration was thought necessary.
    ALTERNATIVE OPERATIVE TREATMENT
    There are no alternative operative solutions other than revision surgery. Surgical options include revision to another intercalary prosthesis , re-cementation of the loose prosthesis or revision to a custom distal humeral endoprosthesis. Amputation would be indicated for a tumour in the distal humerus with neuromuscular involvement that would either compromise adequate tumour resection or leave a flail limb with vascular compromise.
    NON-OPERATIVE MANAGEMENT
    Non-operative management (analgesia and immobilisation in a sling) had failed in this case.
    CONTRAINDICATIONS
    Contraindications to revision surgery include prosthetic joint infection and medical co-morbidity precluding major surgery and anaesthesia.

    Setup

    Operation – 1

    AP radiograph of the left humerus showing satisfactory integration of the proximal portion of the intercalary endoprosthesis, but obvious radiolucencies surrounding the bone cement interface at the distal portion of the modular prosthesis. Additionally no periosteal bone on-growth to the hydroxyapatite-coated extra-cortical plate at the distal end of the prosthesis can be seen. There is minimal residual bone stock distal to the prosthesis for revision surgery.

    Lateral radiograph whole left humerus, again showing obvious radiolucencies at the bone cement interface surrounding the stem of the distal prosthesis.

    CT scan of the proximal portion of the prosthesis showing satisfactory cement-prosthesis and cement-bone interfaces and no obvious loosening of the proximal portion of the prosthesis. This is crucial to confirm that the proximal half of the modular prosthesis can be retained.

    Patient positioning, skin preparation and draping.The patient is positioned supine under general anaesthesia with a supra-clavicular block and empirical intravenous antibiotics. The skin is cleansed twice with alcoholic chlorhexidine skin prep. The whole left upper limb has been excluded with drapes and Ioban incisional surgical drapes applied from the shoulder to the wrist with a bowel bag enveloping the hand (to observe for movements indicating neural damage).

    Longitudinal skin incision over the extensor aspect of the elbow and distal humerus.The skin incision is made over the extensor aspect of the (E) elbow and (DH) distal humerus. In this photograph the posterior aspect of the distal humerus is shown with the elbow flexed and the (F) forearm over the patient’s chest. The skin is incised and dissection is continued with diathermy through the fat to the deep fascia. The skin incision is curved laterally around the tip of the olecranon to optimise wound healing.

    Full thickness skin flaps elevated.The photograph shows the dissection of the fat down to the deep fascia overlying the (T) triceps muscle. Full thickness skin flaps have been elevated and are held apart with a self-retaining retractor. The (O) olecranon process is shown.

    Identify the ulna nerve at the cubital tunnel.Careful blunt dissection around the medial aspect of the elbow identifies the ulna nerve. The full thickness skin flaps have been sutured to keep the skin retracted during the procedure. The ulna nerve is identified medial to (T) triceps and posterior to the inter muscular septum. The nerve arises from the intramuscular septum at arcade of Struthers 8 cm proximal to the medial epicondyle as it passes from the anterior to posterior compartment of the arm and continues into the (C) cubicle tunnel.
    The cubital tunnel is bounded by the flexor carpi ulnaris fascia and Osborne’s ligament (retinaculum traveling from the medial epicondyle to the (O) olecranon)(Roof), the posterior and transverse bands of MCL and elbow joint capsule (floor) and the medial epicondyle and olecranon process (walls). The FCU has two heads raising from the medial epicondyle (humeral head) and the (O) olecranon process (ulna head).

    Sloop the ulna nerve to aid dissection of the nerve to mobilise it away from the distal humerus.After identification of the ulna nerve a surgical sloop is placed around the nerve to enable the nerve to be elevated to permit dissection of the nerve from the distal humerus.

    Dissection of the (U) ulna nerve continues proximally along the medial aspect of the distal humerus to free the ulna nerve from the arcade of Struthers proximally (a hiatus in medial inter-muscular septum).

    The ulna nerve has now been completely mobilised and is free from the soft tissues so that it can be protected during the rest of the operation.

    Elevate the triceps muscle off the distal humerus.Dissection now occurs on the lateral side of the elbow joint. Diathermy is used to release (T) triceps from the posterior distal humerus. The radial nerve lies in the anterior compartment at this level and is not at risk at this stage of the procedure.

    Dissection then continues to elevate the (T) triceps tendon away from the distal humerus so that the tendon can be maintained in continuity as it inserts onto the (O) olecranon process of the proximal ulna.

    Osteotomise the lateral epicondyle to preserve the common extensor origin.The (T) triceps is retracted medially. Using a reciprocating saw a slither of bone is cut from the lateral condyle (LE) of the distal humerus where the common extensor origin is located. The common extensor tendon that originates from the lateral epicondyle of the elbow includes the origins of extensor carpi radialis brevis (ECRB) and longus (ECRL), extensor digitorum communis, extensor digiti minimi, and extensor carpi ulnaris.

    An osteotome is used to complete the osteotomy of the lateral epicondyle and common extensor origin.

    With the osteotomy complete and retraction of the lateral epicondyle and common extensor origin as shown, the radiocapitellar joint is opened. Here the (C) capitellum and the (RH) radial head can clearly be visualised.

    Elevate the the brachialis muscle off the anterior distal humerus.On the medial side the (U) ulna nerve, (O) olecranon and (T) triceps are shown and retracted. Anteriorly, the plane between the brachialis and the (DH) distal humerus is dissected to elevate the muscle from the distal humeral bone proximally to the intercalary implant. Diathermy is used to elevate the muscle in the subperiosteal plane.

    Sub-periosteal dissection of the lateral dial humerus to avoid damage to the radial nerve.On the lateral side, dissection is continued subperiosteally up the lateral column of the distal humerus to identify the extra cortical plate of the loose prosthesis. Here the hydroxyapatite coated (C) collar of the prosthesis has been revealed distal to the shaft of the endoprosthesis. One of the locking screws is just visualised.
    Care is taken not to damage the radial nerve which emerges from the spiral groove between the lateral and medial heads of triceps on the lateral aspect of the humerus, pierces the lateral inter-muscular septum 8-12 cm proximal to the lateral epicondyle (never less than 7.5cm) and enters the anterior compartment of the arm. It then continues distally between brachialis and brachioradialis giving branches to supply the lateral half of brachialis, brachioradialis, ECRL, ECRB before entering the lateral antecubital fossa. It then passes anteriorly to the lateral epicondyle and continues into the forearm to become the superficial radial nerve and posterior interosseous nerve (terminal branches). By dissecting subperiosteally to brachialis and having osteotomised the lateral epicondyle, the radial nerve should be protected.

    Osteotomise the medial epicondyle to preserve the common flexor origin.On the medial side, with the ulna nerve carefully retracted, the (ME) medial epicondyle is osteotomised using a reciprocating saw to preserve the common flexor origin for reattachment to the new implant. The common flexor origin serves as the origin for the forearm flexor muscles including pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis and flexor carpi ulnaris.

    The (U) ulna nerve and the adjacent osteotomy of the (ME) medial epicondyle can be seen distally. Proximal to this the subperiosteal dissection of the residual (DH) distal humerus down to the hydroxyapatite (C) collar of the loose intercalary prosthesis is shown. The chemical formula of hydroxyapatite is Ca10(PO4)6(OH)2.

    A screwdriver is used to remove the two bolts which connect the proximal and distal halves of the intercalary prosthesis.

    Explant the loose distal half of the intercalary endoprosthesis and distal humerus.After removing the bolts and by retracting the triceps laterally the distal humerus can now be removed.

    The distal humerus has been removed with the loose half of the intercalary endoprosthesis shown. The (LC) lateral cortical plate can be seen in the photograph. The proximal and secure half of the intercalary prosthesis remains in the proximal humerus.

    The custom distal humeral endoprosthesis is shown on the back table adjacent to the excised distal humerus. It can be seen that the proximal portion of the prosthesis is identical to the excised and loose prosthesis for reattachment in vivo. The grey purple colour of the prosthesis proximally is the silver coating to minimise the risk of prosthetic infection. Distally the prosthesis has holes for reattachment of the medial and lateral epicondyles and the prosthesis has a new capitellum and hemiarthroplasty for the new humero-ulnar joint.

    Insert the new custom distal humeral endoprosthesis.The prosthesis is inserted and docks with the proximal portion and two new bolts are inserted to fix the proximal and distal portions of the prosthesis together.

    Reduce the humero-ulna joint.The (T) triceps and (O) olecranon process of the ulna are reduced and on the medial side it can be seen that the ulna and implant are articulating.

    Operation – 2

    On the lateral side the new (C) capitellum is visualised with the reduced hemiarthroplasty joint, the (T) triceps and (O) olecranon.

    Suture repair the common extensor origin to the endoprosthesis.Using 3.0 Ethibond sutures the lateral epicondyle and the common extensor origin is sutured to the distal humeral endoprosthesis using the holes on the prosthesis shown in the photograph.

    The lateral epicondyle and the common extensor origin have been attached to the prosthesis.

    Suture repair the common flexor origin to the endoprosthesis.On the medial side, 3.0 Ethibond is again used to reattach the medial epicondyle and common flexor origin to the distal humeral endoprosthesis. The (U) ulna nerve can be seen as it runs in to the FCU.

    The common flexor origin has been reattached to the medial side of the prosthesis and there is now adequate soft tissue coverage around the medial side of the prosthesis.

    Layered closure of full thickness skin flaps. The full thickness skin flaps are now closed in layers using interrupted 1.0 Vicryl sutures.

    Skin closure. The subcutaneous layer is closed with a continuous 0 vicryl suture.

    Apply dressings. After clips are applied to the skin, and aquacel dressing is applied to the extensor aspect of the arm. A sling is applied.

    Post-operative AP radiograph of the distal humeral endoprosthesis showing a reduced humero-ulna hemiarthroplasty. Careful radiological follow-up is required to ensure that the joint does not sublux during rehabilitation.

    Lateral post-op radiograph showing that the neo-distal humeral joint is reduced. Again, careful follow-up is required to ensure the joint doesn’t sublux during rehab. In the long-term, observation for aseptic loosening of the proximal bone-cement interface is required as this is the principle cause of failure of distal humeral endoprostheses.

    Post Operative

    24-hours of post-operative intravenous antibiotics.
    Passive exercises supervised by physiotherapy for flexion and extension for the first two weeks out of a sling only. After two weeks can progress to active elbow flexion and after six weeks can progress to active elbow extension.
    Removal of clips at two weeks.

    Recommended Reading

    There is limited data concerning the outcomes after distal humeral endoprostheses as they are such rare implants. Kulkarni et al. reported the outcomes of ten patients with such implants undertaken during a 30 year period in a single centre; after mean 8 years follow-up, three were revised for aseptic loosening but there were no other failures (https://online.boneandjoint.org.uk/doi/pdf/10.1302/0301-620X.85B2.13524).
    Endoprosthetic replacement of the distal humerus is one way of reconstructing the elbow after excision of a bone tumour. The advantages are immediate stability and the early return of function. The potential disadvantages include the likelihood of failure of the prosthesis at some stage either by wear of the bushes, loosening, infection or fracture. There are few reports of alternative allograft reconstruction of the distal humerus. The only other surgical alternative is above elbow amputation. Non-operative options may include definitive radiotherapy in radiosensitive tumours if surgery not indicated by multiple osseous metastases (e.g. Ewing’s sarcoma)
    We would never advocate heavy load lifting or resistance gym exercises and would advocate functional (activities of daily living) rehabilitation goals.
    Endoprosthetic replacement of the distal humerus is one way of reconstructing the elbow after excision of a bone tumour. The advantages are immediate stability and the early return of function. The potential disadvantages include the likelihood of failure of the prosthesis at some stage either by wear of the bushes, loosening, infection or fracture. There are few reports of alternative allograft reconstruction of the distal humerus. The only other surgical alternative is above elbow amputation. Non-operative options may include definitive radiotherapy in radiosensitive tumours if surgery not indicated by multiple osseous metastases (e.g. Ewing’s sarcoma)
    We would never advocate heavy load lifting or resistance gym exercises and would advocate functional (activities of daily living) rehabilitation goals.

    Reference

    • orthoracle.com

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